Apparatus and methods for plasma vapor deposition processes

ABSTRACT

One aspect of the invention is directed toward a method of forming a conductive layer on a microfeature workpiece. In one embodiment, the method comprises depositing an electrically conductive material onto a first microfeature workpiece in a vapor deposition process by flowing a gas into a plasma zone of a vapor deposition chamber and transmitting an energy into the plasma zone via a transmitting window. The energy transmitted through the window and into the plasma zone produces a plasma from the gas. The energy, for example, can be microwave radiation. The plasma produced from the gas forms a conductive layer on the workpiece in either a CVD or an ALD process. The process of forming the conductive layer on the workpiece concomitantly forms a secondary deposit of a residual film on the window. The residual film has a first transmissivity to the energy used to generate the plasma. This embodiment of the method further includes changing the residual film on the window to have a second transmissivity to the energy. The second transmissivity, for example, can be less than the first transmissivity such that changing the residual film to have the second transmissivity increases the amount of plasma energy that can propagate through the window and into the plasma zone.

TECHNICAL FIELD

The present invention relates to plasma vapor deposition processes used to deposit layers of conductive materials or other types of materials in the fabrication of microfeature devices.

BACKGROUND

Thin film deposition techniques are widely used to build interconnects, plugs, gates, capacitors, transistors and other microfeatures in the manufacturing of microelectronic devices. Thin film deposition techniques are continually improved to meet the ever increasing demands of the industry because the microfeature sizes are constantly decreasing and the number of microfeature layers is constantly increasing. As a result, the density of microfeatures and the aspect ratios of depressions (e.g., the ratio of the depth to the size of the opening) are increasing. Thin film deposition techniques accordingly strive to produce highly uniform conformal layers that cover the sidewalls, bottoms, and corners in deep depressions that have very small openings.

One widely used thin film deposition technique is chemical vapor deposition (CVD). In a CVD system, one or more reactive precursors are mixed in a gas or vapor state and then the precursor mixture is presented to the surface of the workpiece. The surface of the workpiece catalyzes a reaction between the precursors to form a solid, thin film at the workpiece surface. A common way to catalyze the reaction at the surface of the workpiece is to heat the workpiece to a temperature that causes the reaction. CVD processes are routinely employed in many stages of manufacturing microelectronic components.

Atomic layer deposition (ALD) is another thin film deposition technique that is gaining prominence in manufacturing microfeatures on workpieces. FIGS. 1A and 1 B schematically illustrate the basic operation of ALD processes. Referring to FIG. 1A, a layer of gas molecules A coats the surface of a workpiece W. The layer of A molecules is formed by exposing the workpiece W to a precursor gas containing A molecules and then purging the chamber with a purge gas to remove excess A molecules. This process can form a monolayer of A molecules on the surface of the workpiece W because the A molecules at the surface are held in place during the purge cycle by physical adsorption forces at moderate temperatures or chemisorption forces at higher temperatures. The layer of A molecules is then exposed to another precursor gas containing B molecules. The A molecules react with the B molecules to form an extremely thin layer of solid material C on the workpiece W. Such thin layers are referred to herein as nanolayers because they are typically less than 1 nm thick and usually less than 2 Å thick. For example, each cycle may form a layer having a thickness of approximately 0.5-1.0 Å. The chamber is then purged again with a purge gas to remove excess B molecules.

Another type of CVD process is plasma CVD in which energy is added to the gases inside the reaction chamber to form a plasma. U.S. Pat. No. 6,347,602 discloses several types of plasma CVD reactors. FIG. 2 schematically illustrates a conventional plasma processing system including a processing vessel 2 and a microwave transmitting window 4. The plasma processing system further includes a microwave generator 6 having a rectangular wave guide 8 and a disk-shaped antenna 10. The microwaves radiated by the antenna 10 propagate through the window 4 and into the processing vessel 2 to produce a plasma by electron cyclotron resonance. The plasma causes a desired material to be coated onto a workpiece W.

Although plasma CVD processes are useful for several applications, such as gate hardening, they are difficult to use in depositing conductive materials onto the wafer. For example, when the precursors are introduced into the chamber to create a metal layer, a secondary deposit of the metal accumulates on the interior surface of the window 4. This secondary deposit of metal builds up on the window 4 as successive microfeature workpieces are processed. One problem is that the secondary deposit of metal has a low transmissivity to the microwave energy radiating from the antenna 10. After a period of time, the secondary deposit of metal can block the microwave energy from propagating through the window 4 and into the processing vessel 2. The secondary deposit of metal is also generally non-uniform across the interior surface of the window 4. Therefore, the secondary deposit of metal on the window 4 can prevent the plasma from forming or produce non-uniform films on the workpiece.

To reduce the effects of the secondary deposit of metal on the window 4, the interior of the reaction chamber must be cleaned periodically. For example, flowing ClF₃ through the processing vessel 2 is one possible process to clean the window 4. This process, however, requires that the reaction chamber be cooled from a deposition temperature of approximately 400° C. to a cleaning temperature of approximately 300° C. The chamber is then purged of the cleaning agent and reheated back to the 400° C. deposition temperature. The cleaning process generally requires 3-4 hours to complete, and it may need to be performed frequently when depositing a metal onto the workpiece. Moreover, even after purging the cleaner from the chamber, residual molecules of the cleaner may remain in the chamber and contaminate the resulting film or otherwise disrupt the deposition process. Therefore, it has not been economical to use plasma vapor deposition processes for depositing certain types of metal layers or other conductive materials on microfeature workpieces.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic cross-sectional views of stages in ALD processing in accordance with the prior art.

FIG. 2 is a schematic cross-sectional view of a plasma vapor deposition system in accordance with the prior art.

FIG. 3 is a schematic cross-sectional view of a plasma vapor deposition system in accordance with an embodiment of the invention.

FIG. 4 is a flow chart of a method in accordance with an embodiment of the invention.

FIGS. 5A and 5B are schematic cross-sectional views of a portion of a transmitting window used in a plasma vapor deposition system at various stages of an embodiment of a method in accordance with the invention.

DETAILED DESCRIPTION

A. Overview

Various embodiments of the present invention provide workpiece processing systems and methods for depositing materials onto microfeature workpieces. Many specific details of the invention are described below with reference to systems for depositing metals or other conductive materials onto microfeature workpieces, but the invention is also applicable to depositing other materials (e.g., dielectrics that have a low transmissivity to the plasma energy). The term “microfeature workpiece” is used throughout to include substrates upon which and/or in which microelectronic devices, micromechanical devices, data storage elements, read/write components, and other features are fabricated. For example, microfeature workpieces can be semiconductor wafers (e.g., silicon or gallium arsenide wafers), glass substrates, insulative substrates, and many other types of materials. The microfeature workpieces typically have submicron features with dimensions of a few nanometers or greater. Furthermore, the term “gas” is used throughout to include any form of matter that has no fixed shape and will conform in volume to the space available, which specifically includes vapors (i.e., a gas having a temperature less than the critical temperature so that it may be liquefied or solidified by compression at a constant temperature). Several embodiments in accordance with the invention are set forth in FIGS. 3-5B and the following text to provide a thorough understanding of particular embodiments of the invention. A person skilled in the art, however, will understand that the invention may have additional embodiments, or that the invention may be practiced without several of the details of the embodiments shown in FIGS. 3-5B.

One aspect of the invention is directed toward a method of forming a conductive layer on a microfeature workpiece. In one embodiment, the method comprises depositing an electrically conductive material onto a first microfeature workpiece in a vapor deposition process by flowing a gas into a plasma zone of a vapor deposition chamber and transmitting an energy into the plasma zone via a transmitting window. The energy transmitted through the window and into the plasma zone produces a plasma from the gas. The energy, for example, can be microwave radiation. The plasma produced from the gas forms a conductive layer on the workpiece using either CVD or ALD processes. The process of forming the conductive layer on the workpiece secondarily deposits a residual film on the window. The residual film has a first transmissivity to the plasma energy. This embodiment of the method further includes changing the residual film on the window to have a second transmissivity to the plasma energy. The second transmissivity to the plasma energy, for example, can be less than the first transmissivity. As such, changing the residual film to have a second transmissivity to the energy increases the amount of plasma energy that can propagate through the window and into the plasma zone.

Additional aspects of the invention are directed toward particular procedures for changing the residual film on the window to have the second transmissivity to the plasma energy. When the residual film is a conductive material, the procedure of changing the residual film to have a second transmissivity comprises transforming the conductive material on the window into a substantially dielectric material. For example, one embodiment comprises transforming the conductive material on the window into a substantially dielectric material by changing the conductive material to an oxide. Several suitable conductive materials that can be deposited on the workpiece and secondarily deposited on the window include Ti, Cu, Al, Ni and/or Co; all of these materials can be oxidized to become dielectric materials with a higher transmissivity to the plasma energy than they have in a non-oxidized state.

In still another aspect of the invention, the residual film of material secondarily deposited onto the window is changed or transformed to have a different transmissivity at a temperature that is at least relatively close to the temperature at which the material is deposited. For example, when a conductive material is deposited onto the workpiece and secondarily deposited onto the window at a deposition temperature, the electrically conductive material can be transformed into a substantially dielectric material at a maintenance temperature of approximately 80% to 120% of the deposition temperature. In other embodiments, the maintenance temperature is approximately 95% to 105% of the deposition temperature, or in still other embodiments the maintenance temperature is approximately equal to the deposition temperature. In several embodiments, the maintenance temperature can be within approximately 50° C. of the deposition temperature.

Still another aspect of the invention is directed toward an apparatus for depositing a material onto a microfeature workpiece. In one embodiment, the apparatus includes a reaction chamber having a workpiece holder and a plasma zone, an energy source configured to generate and direct a plasma energy toward the plasma zone, and a transmitting window through which the plasma energy can propagate from the energy source to the plasma zone. The apparatus further includes a controller coupled to a process gas unit and a maintenance gas unit. The process gas unit and the maintenance gas unit may be part of a single gas source system coupled to the reaction chamber. The controller contains computer operable instructions that cause: (a) a first gas and/or a second gas to be injected into the chamber in a manner that forms a conductive material on the workpiece; and (b) a maintenance gas to be injected into the chamber to increase the energy transmissivity of residual conductive material deposited on the window.

For ease of understanding, the following discussion is divided into two areas of emphasis. The first section discusses aspects of vapor deposition processing systems that may be used in accordance with selected embodiments of the invention. The second section outlines methods in accordance with embodiments of the invention.

B. Embodiments of Plasma Vapor Deposition Systems for Fabricating Microfeatures on a Workpiece

FIG. 3 is a schematic cross-sectional view of a plasma vapor deposition system 100 for depositing a material onto a microfeature workpiece. In this embodiment, the deposition system 100 includes a reactor 110, a gas supply 170 configured to produce and/or contain gases, and a controller 190 containing computer operable instructions that cause the gas supply 170 to selectively deliver one or more gases to the reactor 110. The deposition system 100 can perform CVD, ALD, and/or pseudo ALD processes.

The deposition system 100 is suitable for plasma vapor deposition of several different types of materials, and it has particular utility for depositing conductive materials using microwave energy to generate a plasma in the chamber 110. To date, it has been difficult to deposit certain metals or other conductive materials without using a plasma enhanced system because one or more precursors may need additional energy to cause the reaction that forms the thin conductive film. Although prior art plasma vapor deposition systems provide the additional energy to cause the necessary reaction, they also secondarily deposit the conductive material onto the interior surface of the reactor 110. The secondary deposition of the conductive material on the interior surfaces of the reaction chamber impedes the microwave energy from entering the reaction chamber and forming the plasma. The prior art plasma vapor deposition chambers are thus unsuitable for depositing many metals. As explained in more detail below, the deposition system 100 resolves this problem by transforming the secondarily deposited material on the interior surfaces of the reactor 110 into a material that has a sufficient transmissivity to the microwave energy or other type of plasma energy. Several embodiments of the vapor deposition system 100, moreover, can transform the secondarily deposited material without having to significantly cool or otherwise shut down the deposition system 100.

Referring to the embodiment of the deposition system 100 shown in FIG. 3, the reactor 110 includes a reaction chamber 120, a gas distributor 122 coupled to the gas supply 170, a workpiece holder 124 for holding a workpiece W, and a plasma zone 126 where a plasma can be generated. The gas distributor 122 can be an annular antechamber having a plurality of ports for injecting or flowing the gases G into the reaction chamber 120. More specifically, the gas distributor 122 can be a manifold having a plurality of different conduits so that individual gases are delivered into the plasma zone 126 through dedicated ports.

The reactor 110 can further include a window 130 having a first surface 132 and a second surface 134. The window 130 can be a plate or pane of material through which energy propagates into the reaction chamber 120 to generate a plasma in the plasma zone 126. The window 130 accordingly has a high transmissivity to the plasma energy that generates the plasma. For example, when microwave energy is used to generate the plasma, the window 130 can be a quartz plate or other material that readily transmits microwaves.

The reactor 110 further includes an energy system having a generator 140 for generating a plasma energy, an energy guide 142 coupled to the generator 140, and an antenna 144 or other type of transmitter coupled to the energy guide 142. The generator 140 can be a microwave generator. For example, the generator 140 can produce microwave energy at 2.45 GHz or another frequency suitable for producing a plasma in the plasma zone 126. The generator 140 generates a plasma energy E that propagates through the energy guide 142 to the antenna 144, and the antenna 144 transmits the plasma energy E through the window 130 to the plasma zone 126.

Referring still to FIG. 3, the gas supply 170 can include a process gas module 172, a maintenance fluid module 174, and a valve system 176. The process gas module 172 can include a plurality of individual gas units 180 (identified by reference numbers 180 a-c) for containing or producing process gases. In one embodiment, the process gas module 172 includes a first gas unit 180 a for a first process gas PG₁, a second gas unit 180 b for a second process gas PG₂, and a third gas unit 180 c for a third process gas PG₃. The first process gas PG₁ can be a first precursor gas and the second process gas PG₂ can be a second precursor gas selected to react with each other to form the layer of material on the workpiece W. The third process gas PG₃ can be a purge gas, such as argon, for purging the first process gas PG, and/or the second process gas PG₂ from the reaction chamber 120 in ALD or CVD processes. The process gas module 172 is not limited to having three gas units 180 a-c, but rather it can have any number of individual gas units required to provide the desired precursors and/or purge gases to the gas distributor 122. As such, the process gas module 172 can include more or fewer precursor gases and/or purge gases than shown on FIG. 3.

The maintenance fluid module 174 can include one or more maintenance fluids. At least one maintenance fluid MF₁ is selected to transform the conductive material produced by the reaction of the first and second process gases PG₁ and PG₂ into a benign material that is suitably transmissive to the plasma energy E in a preferred embodiment of the invention. The interaction between the maintenance fluid MF₁ and the process gases PG₁-PG₃ is explained in more detail below with reference to FIGS. 4-5B.

The controller 190 is coupled to the valve system 176. The controller 190 can also be coupled to the generator 140 and other components of the vapor deposition system 100, or additional controllers may be included to operate other components. The controller 190 can be a computer containing computer operable instructions in the form of hardware and/or software for controlling the valve system 176 in a manner set forth below with reference to the various methods discussed in FIGS. 4-5B.

C. Embodiments of Methods for Plasma Vapor Deposition of Conductive Material on Microfeature Workpieces [0027] FIG. 4 is a flow chart of a plasma vapor deposition method 400 for forming a conductive layer on a microfeature workpiece in accordance with an embodiment of the invention. The method 400 includes a plasma vapor deposition procedure 402 and a maintenance procedure 404. The plasma vapor deposition procedure 402 and the maintenance procedure 404 can be performed in the deposition system 100 shown in FIG. 3. The operation of the deposition system 100 shown in FIG. 3 in accordance with the method 400 shown in FIG. 4 enables the efficient use of plasma vapor deposition processes to deposit thin conductive films, such as titanium, on advanced microfeature workpieces that have very small feature sizes and high densities of features. Several embodiments of the plasma vapor deposition procedure 402 and the maintenance procedure 404 will be discussed below with reference to the plasma vapor deposition 100 system of FIG. 3.

One embodiment of the plasma vapor deposition procedure 402 comprises generating a plasma from a gas injected into the plasma zone 126 of the reaction chamber 120. For example, the controller 190 can cause the valve system 176 to inject a process gas into the plasma zone 126 via the gas distributor 122 while the generator 140 generates microwaves at a frequency selected to excite the molecules of the process gas to create a plasma. In a CVD process, the controller 190 operates the valve system 176 to inject the first and second process gases PG₁ and PG₂ into the plasma zone 126 concurrently. The first and second process gases PG₁ and PG₂ can be mixed in the gas distributor 122 or in the plasma zone 126 in CVD applications. In an ALD process, the controller 190 operates the valve system 176 to inject discrete pulses of the first and second process gases PH₁ and PG₂ into the plasma zone 126 at separate times. The controller 190, for example, can operate the valve assembly 176 to repeatedly produce a pulse train having pulses PG₁-PG₃-PG₂-PG₃; the first and second process gases PG₁ and PG₂ can be reactive precursors, and the third process gas PG₃ can be a purge gas. The plasma is generated from one or both of the first and second process gases PH₁ and PG₂ to form the conductive material. Referring to FIG. 5A, the conductive material formed from the plasma vapor deposition procedure 402 forms a residual film 198 on the second surface 134 of the window 130. In the case of depositing a conductive material comprising Ti, Cu, Al, Ni and/or Co, the residual film 198 on the window 130 blocks or impedes a substantial portion of the plasma energy E from entering the plasma zone 126.

The maintenance procedure 404 accordingly changes the residual film 198 on the second surface 134 of the window 130 to have a different transmissivity to the plasma energy E. In one embodiment, the maintenance procedure 404 involves increasing the transmissivity of the residual film 198 to be more transmissive to the plasma energy E. For example, the transmissivity of the residual film 198 can be increased by transforming the conductive material into a substantially dielectric material. When the conductive material comprises at least one of Ti, Cu, Al, Ni and/or Co, it can be transformed into a substantially dielectric material by an oxidizing process. In other embodiments, tungsten (w), nitrides (e.g., TiN, WN, etc.), borides, sulfides and carbides deposited on the wafer can form a residual film on the window 130, and then these materials can be transformed to be more transmissive to the plasma energy by an oxidization process or another process.

One specific embodiment of the maintenance procedure 404 includes injecting the maintenance fluid MF₁ into the reaction chamber 120 after terminating the plasma vapor deposition procedure 402 and removing the workpiece W from the reactor 110. In this embodiment, the controller 190 causes the valve system 176 to terminate the flows of the process gases PG₁-PG₃ and to initiate the flow of the maintenance fluid MF₁. Referring to FIG. 5B, the flow of maintenance fluid MF₁ transforms the residual film 198 into a benign film 199 that is more transmissive to the plasma energy E. The maintenance fluid MF₁ can comprise a fluid containing oxygen atoms or molecules, such as O₂, ozone, water, alcohol, etc.

The maintenance procedure 404 can be performed at a temperature approximately equal to the temperature of the plasma vapor deposition procedure 402. For example, if the plasma vapor deposition procedure 402 occurs at a process temperature T₁, then the maintenance procedure 404 can occur at a maintenance temperature T₂ approximately 80-120% of T₁. In other embodiments, the maintenance temperature T₂ can be 95-105% of T₁, or in still other embodiments the maintenance temperature T₂ can be approximately equal to T₁. In general, the maintenance temperature T₂ should be within approximately 50° C. of T₁ to limit the amount of time to cool/heat the reaction chamber 120 between the vapor deposition procedure 402 and the maintenance procedure 404.

The maintenance procedure 404 can be performed between each wafer or after a plurality of wafers have been processed through the vapor deposition system 100. For example, the controller 190 can operate the valve system 176 to deposit a conductive film on a plurality of wafers in a single-wafer process before the controller 190 stops the plasma vapor deposition procedure 402 and initiates the maintenance procedure 404.

One specific application of the plasma vapor deposition system 100 shown in FIG. 3 and the method 400 illustrated in FIGS. 4-5B is to deposit a titanium film using TiCl₄ 3nd H₂ in an ALD process. A titanium film can be formed using an ALD process in which the first process gas PG₁ is TiCl₄, the second process gas PG₂ is H₂, and the third process gas PG₃ is argon or another purge gas. In this embodiment, the controller 190 effectuates the plasma vapor deposition procedure 402 by operating the valve system 176 to repeatedly inject a pulse train of TiCl₄ (PG₁), purge gas (PG₃), H₂ (PG₂), and purge gas (PG₃). The H₂ forms a plasma of hydrogen molecules as it is injected into the plasma zone 126. The unilayers of TiCl₄ on the workpiece W react with the hydrogen atoms from the plasma at the surface of the workpiece to create a titanium film across the workpiece. After the titanium film reaches a desired thickness, the workpiece W is removed from the reaction chamber 120 and the controller 190 operates the valve system 176 to initiate the maintenance procedure 404. More specifically, the controller 190 operates the valve system 176 to inject a maintenance fluid MF₁ containing oxygen into the reaction chamber 120 to transform the residual Ti film on the second surface 134 of the window 130 to titanium oxide. The controller 190 can then operate the valve system 176 to terminate the flow of maintenance fluid MF₁ from the maintenance fluid module 174. The maintenance procedure 404 can further include a pump out operation in which a vacuum pump 191 draws the maintenance fluid MF₁ out of the reaction chamber 120. In another embodiment, the maintenance procedure 404 can further include a purge step in which the controller 190 operates the valve system 176 to inject the purge gas PG₃ into the reaction chamber 120 after terminating the flow of the maintenance fluid MF₁ and pumping out the reaction chamber 120.

Another specific application of the plasma vapor deposition system 100 and the method 400 is to deposit a titanium film using TiCl₄ and H₂ in a CVD process or a pulsed CVD process. In this case, the controller 190 operates the valve system 176 so that the TiCl₄ (PG₁) and the H₂ (PG₂) are injected into the reaction chamber 120 simultaneously. The plasma energy E propagating from the antenna 144 generates a plasma from the H₂ molecules, which reacts with the TiCl₄ to form a Ti film across the face of the workpiece W. The controller 190 can continue to process additional wafers through the reaction chamber 120 in a continuation of the deposition procedure 402 until a residual titanium film builds up on the second surface 134 of the window 130 to a degree that it disrupts the plasma energy E from entering the plasma zone 126. The controller 190 can then operate the valve system 176 to initiate a flow of the maintenance fluid MF₁ into the reaction chamber 120 to oxidize or otherwise transform the residual titanium film to be more transmissive to the plasma energy E.

From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims. 

1-24. (canceled)
 25. An apparatus for depositing a material onto a microfeature workpiece, comprising: a reaction chamber including a workpiece holder positioned relative to a plasma zone in the chamber, an energy source configured to generate a plasma energy and direct the plasma energy toward the plasma zone, and a window transmissive of the plasma energy between the energy source and the plasma zone; a process gas supply unit containing first and second process gases selected to react with each other to form a conductive material, wherein the process gas unit is configured to deliver at least one of the first and second gases to the plasma zone to deposit the conductive material on the workpiece; a maintenance gas unit containing a maintenance gas selected to increase a transmissivity of the conductive material formed by reacting the first and second gases to the plasma energy, wherein the maintenance gas unit is configured to deliver the maintenance gas to the window; and a controller coupled to the process gas unit and the maintenance gas unit, the controller containing computer operable instructions causing (a) the first and second gases to be injected into the chamber in a manner that deposits the conductive material onto the workpiece, and (b) the maintenance gas to be injected into the chamber in a manner that increases the transmissivity of the conductive material deposited onto the window to the plasma energy.
 26. The apparatus of claim 25 wherein the conductive material resulting from reacting the first and second process gases comprises a metal, and the maintenance fluid comprises oxygen for transforming the conductive material on the window into a substantially dielectric material by changing the metal to an oxide.
 27. The apparatus of claim 25 wherein the conductive material resulting from reacting the first and second process gases comprises at least one of Ti, Cu, Al, Ni and/or Co, and the maintenance fluid comprises oxygen for transforming the conductive material into a substantially dielectric material comprising an oxide of Ti, Cu, Al, Ni and/or Co.
 28. The apparatus of claim 25 wherein the controller contains computer readable instructions to inject the first and second process gases into the chamber at a deposition temperature and to inject the maintenance fluid into the chamber at a maintenance temperature of approximately 80% to 120% of the deposition temperature.
 29. The apparatus of claim 25 wherein the controller contains computer readable instructions to inject the first and second process gases into the chamber at a deposition temperature and to inject the maintenance fluid into the chamber at a maintenance temperature of approximately 95% to 105% of the deposition temperature.
 30. The apparatus of claim 25 wherein the controller contains computer readable instructions to inject the first and second process gases into the chamber at a deposition temperature and to inject the maintenance fluid into the chamber at a maintenance temperature approximately equal to the deposition temperature.
 31. The apparatus of claim 25 wherein the controller contains computer readable instructions to inject the first and second process gases into the chamber at a deposition temperature and to inject the maintenance fluid into the chamber at a maintenance temperature within approximately 50° C. of the deposition temperature.
 32. An apparatus for depositing a material onto a microfeature workpiece, comprising: a reaction chamber including a workpiece holder positioned relative to a plasma zone in the chamber, an energy source configured to generate a plasma energy and direct the plasma energy toward the plasma zone, and a window transmissive of the plasma energy between the energy source and the plasma zone; and a controller coupled to a process gas unit and a maintenance gas unit, the controller containing computer operable instructions that cause (a) a first gas and a second gas to be injected into the chamber in a manner that deposits a conductive material onto the workpiece and a residual conductive material onto the window, and (b) a maintenance gas to be injected into the chamber in a manner that reacts with the residual conductive material on the window to increase the transmissivity of the residual conductive material to the plasma energy.
 33. The apparatus of claim 32 wherein the conductive material deposited on the workpiece and the window comprises a metal, and the maintenance gas comprises oxygen for transforming the metal into an oxide.
 34. The apparatus of claim 32 wherein the conductive material deposited on the workpiece comprises at least one of Ti, Cu, Al, Ni and/or Co, and the maintenance gas comprises oxygen for transforming the conductive material into an oxide of at least one of the Ti, Cu, Al, Ni and/or Co.
 35. The apparatus of claim 32 wherein the controller contains computer readable instructions to inject the first and second process gases into the chamber at a deposition temperature and to inject the maintenance fluid into the chamber at a maintenance temperature of approximately 80% to 120% of the deposition temperature.
 40. The apparatus of claim 35 wherein the controller contains computer readable instructions to inject the first and second process gases into the chamber at a deposition temperature and to inject the maintenance fluid into the chamber at a maintenance temperature of approximately 95% to 105% of the deposition temperature.
 41. The apparatus of claim 35 wherein the controller contains computer readable instructions to inject the first and second process gases into the chamber at a deposition temperature and to inject the maintenance fluid into the chamber at a maintenance temperature approximately equal to the deposition temperature.
 42. The apparatus of claim 35 wherein the controller contains computer readable instructions to inject the first and second process gases into the chamber at a deposition temperature and to inject the maintenance fluid into the chamber at a maintenance temperature within approximately 50° C. of the deposition temperature. 